IEC 61643 SPD Standards Explained: Part 01 vs 11 vs 21 vs 31 vs 41

The IEC 61643 series does not assign one interchangeable standard to every surge protective device. The applicable part depends on the circuit being protected: IEC 61643-11 covers AC power, IEC 61643-21 covers telecommunications and signalling, IEC 61643-31 covers photovoltaic DC circuits, and IEC 61643-41 covers non-PV DC power. IEC 61643-01 supplies common requirements where the relevant product standard requires it.

That distinction becomes critical when one installation combines AC distribution, solar strings, battery storage, Ethernet communication, and control wiring. A device described simply as “IEC 61643 compliant” may still be inappropriate for the circuit, source characteristics, fault conditions, or standard edition specified for the project.

The following crosswalk reflects the IEC publications available on August 25, 2026.

IEC 61643 Standards Comparison: Which Part Applies?

IEC standard	Published edition	Primary scope	Voltage boundary stated by IEC	Relationship to Part 01	Critical limitation
IEC 61643-01:2024	Edition 1.0	Common SPD requirements, ratings, safety provisions, and test methods	Up to 1,000 V AC RMS or 1,500 V DC	Common foundation; not a replacement for the applicable product-specific part	Part 01 alone does not identify whether a device is suitable for AC, PV DC, other DC, or data lines.
IEC 61643-11:2025	Edition 2.0	SPDs connected to low-voltage переменным током (AC) circuits and equipment	Up to 1,000 V AC RMS; preferred frequencies 50/60 Hz	Must be read and applied with the latest edition of IEC 61643-01, as referenced by Part 11	The 2025 edition is AC-specific; it is not the product standard for PV strings or ordinary DC power circuits.
IEC 61643-21:2025	Edition 2.0	SPDs connected to telecommunications and signalling networks, including lines that also carry power	Up to 1,000 V RMS and 1,500 V DC within the stated network scope	Used in conjunction with IEC 61643-01:2024	A DC voltage on a communications cable does not automatically make it a Part 41 power circuit.
IEC 61643-31:2018	Edition 1.0; IEC copy incorporates the June 2022 corrigendum	SPDs dedicated to the DC side of PV generators and inverters	Up to 1,500 V DC	The published 2018 scope does not state the same Part 01 pairing requirement as the 2025 editions of Parts 11, 21, and 41	Excludes SPDs for PV systems with energy storage, such as batteries or capacitor banks.
IEC 61643-41:2025	Edition 1.0	SPDs connected to low-voltage DC power circuits and equipment	Up to 1,500 V DC	Used in conjunction with IEC 61643-01	Explicitly excludes SPDs for photovoltaic applications, which fall under Part 31.

The edition and scope information comes from the official IEC publications for IEC 61643-01:2024, IEC 61643-11:2025, IEC 61643-21:2025, IEC 61643-31:2018, и IEC 61643-41:2025.

Engineering rule: Identify the function and electrical environment of the protected circuit before comparing voltage, discharge-current ratings, product type, or price.

For a broader introduction to protection devices and their operating principles, see what a surge protection device is and how it protects electrical systems.

Start With the Circuit, Not the SPD Label

A useful standards-selection sequence is:

1. Is the protected circuit an AC power circuit? Start with IEC 61643-11:2025 and its applicable IEC 61643-01 requirements.
2. Is it the DC side of a photovoltaic generator or the PV-side DC connection of an inverter? Start with IEC 61643-31:2018 and verify the actual application remains within that edition’s scope.
3. Is it a non-PV DC power circuit? Start with IEC 61643-41:2025 and IEC 61643-01, then check source behavior, fault current, and any application-specific requirements.
4. Is it a telecommunications, Ethernet, instrumentation, or signalling circuit? Start with IEC 61643-21:2025 and IEC 61643-01:2024, even when the same communication line also carries power.

Это scope-screening tool, not a declaration that every device satisfying a given standard will fit every circuit inside that category. System voltage, maximum continuous operating voltage, protection modes, prospective short-circuit current, temporary overvoltage behavior, backup protection, environmental conditions, and local installation rules still require separate verification.

IEC 61643-01: The Common Requirements Foundation

IEC 61643-01:2024 establishes common requirements and test methods for low-voltage surge protective devices connected to circuits or equipment up to 1,000 V AC RMS or 1,500 V DC. Its published scope addresses shared performance and safety requirements rather than defining a single universal application category.

According to the official IEC 61643-01 publication, notable technical areas include:

• Whether testing applies to a complete SPD, an individual mode of protection, or a complete SPD assembly.
• Voltage protection level across combined protection modes.
• Additional duty testing for certain Type 1 and Type 2 SPDs with follow current.
• Revised short-circuit test requirements reflecting internal disconnector technologies.
• Dielectric and clearance requirements for electrically separated circuits.
• Additional information relevant to DC installations.

The practical implication is that Part 01 is a common technical layer, not an application selector. A procurement requirement that says only “IEC 61643-01” does not establish whether the SPD has been assessed for AC distribution, telecommunications, photovoltaic generator circuits, or non-PV DC power.

Which IEC 61643 Parts Explicitly Require Part 01?

The answer depends on the wording and edition of the application-specific standard:

• Part 11:2025: Its published scope states that its requirements supplement, modify, or replace requirements in Part 01 and must be read and applied with the latest edition of Part 01 referenced by its undated normative reference.
• Part 21:2025: Its published scope explicitly says it is used in conjunction with IEC 61643-01:2024.
• Part 41:2025: Its published scope explicitly says it is used in conjunction with IEC 61643-01.
• Part 31:2018: The currently published PV-specific edition predates Part 01:2024, and its public IEC scope does not state an equivalent requirement to apply Part 01.

Therefore, it is accurate to describe Parts 11, 21, and 41 in their cited editions as application-specific standards working with Part 01. It is нет accurate to impose a blanket “Part 31:2018 + Part 01:2024” requirement unless the applicable adoption, updated edition, certification scheme, project specification, or product documentation explicitly establishes that relationship.

This distinction matters when reviewing existing solar-product certificates. An older but applicable PV standard should not be represented as referencing a common standard published several years afterward without documented evidence.

IEC 61643-11: AC Low-Voltage Power Systems

IEC 61643-11:2025 applies to SPDs connected to AC power circuits and equipment rated up to 1,000 V RMS. The preferred frequencies addressed are 50 Hz and 60 Hz, while the published scope notes that other frequencies are not automatically excluded.

Common circuit examples include:

• Main incoming AC distribution boards.
• Industrial switchboards and commercial distribution panels.
• AC feeder and subdistribution circuits.
• The AC output side of a photovoltaic inverter.
• The AC grid-connection side of an energy-storage installation.
• Appropriate AC supply points serving electrical equipment or EV charging infrastructure.

Part 11’s scope does нет mean every AC SPD is suitable for every AC network. Selection still depends on system voltage, earthing arrangement, protection modes, temporary overvoltage behavior, prospective fault current, device ratings, backup protection, and manufacturer instructions.

The IEC also cautions that its stated test assumptions are based on an AC power source with a linear voltage-current characteristic. Different source behavior, frequencies, or unusual fault conditions may require additional evaluation.

What Changed in the 2025 Edition?

The 2025 edition separates AC-specific requirements from the common requirements now contained in Part 01. The official publication also identifies changes involving combined protection modes, follow-current duty, short-circuit tests, disconnectors, dielectric performance, and electrically separated circuits.

For purchasing and specification, the key change is straightforward: “IEC 61643-11” without an edition is incomplete information. A document referencing an earlier edition may not represent the same standards structure as a report referencing IEC 61643-11:2025 together with the applicable Part 01 requirements.

For a dedicated interpretation of the AC product standard, see IEC 61643-11 and surge protective devices for low-voltage power systems.

IEC 61643-21: Telecommunications, Signalling, and PoE

IEC 61643-21:2025 covers SPDs connected to telecommunications and signalling networks and associated equipment. Its stated scope extends up to 1,000 V RMS and 1,500 V DC within those network applications.

Типичные примеры включают:

• Ethernet and data-network lines.
• Power over Ethernet connections.
• Industrial instrumentation and signal circuits.
• Communication links serving distributed electrical equipment.
• Appropriate control, monitoring, and telecommunications interfaces.

The critical classification principle is функцией цепи. A PoE connection transfers both communication signals and electrical power, but the current edition of Part 21 explicitly recognizes telecommunications and signalling lines that also provide power. The presence of DC on the line does not, by itself, reclassify the protector as a Part 41 DC-power SPD.

However, compliance with the relevant standard does not establish universal compatibility with every Ethernet installation. The actual protector must also match the interface, connector, line voltage, current, supported data rate, cable category, insertion loss, shielding arrangement, applicable PoE power delivery, and manufacturer-defined operating conditions.

The 2025 second edition replaces the earlier first edition and its amendments and adopts a structure based on IEC 61643-01:2024. The standard’s own published scope explicitly states that the two documents are used together.

For interface-level engineering decisions, use the dedicated signal, data, and control-line surge protector selection guide.

IEC 61643-31: Photovoltaic DC Surge Protection

IEC 61643-31:2018 applies to SPDs intended for the DC side of photovoltaic installations rated up to 1,500 V DC. Its published scope specifically identifies the DC side of photovoltaic generators and the DC side of inverters.

Appropriate scope-screening examples include:

• PV-string protection where the circuit is within the standard and product scope.
• PV combiner-box surge protection.
• PV generator conductors entering an inverter.
• Other dedicated PV-side DC protection positions identified in the product documentation.

This application is distinct from ordinary DC distribution. The electrical behavior of a photovoltaic source, its operating voltage, grounding arrangement, fault conditions, and installation architecture affect the SPD requirements.

Does IEC 61643-31 Cover Battery Storage?

Not as a blanket extension. The official Part 31 scope explicitly states that SPDs for PV systems with energy storage, such as batteries or capacitor banks, are not covered.

This wording does not mean an installation that contains both PV and storage cannot use a PV SPD on a genuinely separate PV-generator circuit. It means engineers cannot treat a Part 31 PV-only declaration as automatic evidence that the same SPD is suitable for a battery-connected or storage-associated DC circuit.

A hybrid system must be assessed circuit by circuit:

• Dedicated PV-generator DC circuit: evaluate Part 31 where its scope genuinely applies.
• Battery or non-PV DC power circuit: evaluate Part 41 and the actual source/fault conditions, where within scope.
• Grid-connected AC circuit: evaluate Part 11.
• Monitoring or communications circuit: evaluate Part 21.

For the practical solar application rather than the standards crosswalk, see how to choose an SPD for a solar power system.

IEC 61643-41: Non-PV DC Low-Voltage Power Systems

IEC 61643-41:2025 establishes requirements and test methods for SPDs connected to DC power circuits and equipment rated up to 1,500 V DC. It must be used in conjunction with IEC 61643-01.

Potential application categories, subject to the actual product and system scope, include:

• Industrial DC distribution circuits.
• Appropriate DC power buses.
• Certain battery-connected or energy-storage power circuits.
• Relevant DC power sections of charging or power-conversion equipment.
• Other non-PV low-voltage DC applications where no more specific applicable product requirements override the selection.

The boundary is explicit: Part 41 excludes SPDs for photovoltaic applications. The IEC identifies Part 31 as the relevant PV-specific product standard.

Why the DC Source Still Matters

The Part 41 test assumptions are based on a DC power source with a linear voltage-current characteristic. Its published scope warns that different source characteristics require careful consideration, particularly regarding expected short-circuit current and temporary overvoltage stresses.

For battery storage, EV charging, and complex converter-fed systems, do not select an SPD by matching nominal DC voltage alone. Verify:

• Maximum continuous operating voltage and polarity requirements.
• Source behavior under normal and fault conditions.
• Prospective short-circuit current and the applicable declared short-circuit withstand/current information, such as I_sccr where relevant; use SCCR only when that designation belongs to the applicable product or market framework.
• Disconnector and backup-protection coordination.
• Temporary overvoltage behavior.
• Protection modes and earthing arrangement.
• Applicable equipment-specific requirements and national installation rules.

An SPD tested or marketed only for a PV source should not be assumed suitable for a battery source simply because both labels show the same DC voltage.

For a system-level breakdown, see BESS surge protection across DC, AC, and signal circuits.

IEC 61643-31 vs. IEC 61643-41: The DC Distinction That Matters

Вопрос	IEC 61643-31	IEC 61643-41
What circuit does the product standard address?	The DC side of PV generators and PV-side inverter connections within the stated scope.	Non-PV low-voltage DC power circuits and equipment within the stated scope.
What is the published DC voltage boundary?	Up to 1,500 V DC.	Up to 1,500 V DC.
Does the published scope cover ordinary battery-storage applications automatically?	No. Its published scope excludes SPDs for PV systems with energy storage such as batteries or capacitor banks.	Battery-connected applications may fall within its DC scope, but source characteristics, fault conditions, other applicable requirements, and exact product documentation must be verified.
Does it cover dedicated photovoltaic SPD applications?	Yes, where the circuit and product remain within the stated PV scope.	No. PV applications are explicitly excluded.
Does the published product standard explicitly invoke Part 01?	The public scope for the 2018 edition does not state the same express relationship.	Yes. Part 41 states that it is used with IEC 61643-01.

The practical rule is not “PV DC versus battery DC based solely on nameplate voltage.” It is source function, circuit location, applicable published scope, fault behavior, and model-specific evidence.

Real Installations Often Need Several IEC 61643 Parts

Hybrid Solar Plant With Battery Storage

Consider a system with PV strings, a hybrid inverter, a battery DC bus, an AC distribution connection, and networked monitoring.

Protected circuit	Starting product-standard assessment	Scope check
Dedicated PV-generator DC input	IEC 61643-31	Confirm the protection position is genuinely a PV-generator/PV-side circuit and that the product is appropriate for the actual arrangement.
Battery-connected DC power circuit	IEC 61643-41 plus IEC 61643-01, where applicable	Assess battery-source behavior, available fault current, disconnectors, backup protection, and any system-specific rules.
Inverter AC output or AC distribution connection	IEC 61643-11 plus the applicable IEC 61643-01 requirements	Verify AC system voltage, earthing arrangement, protection mode, and installation conditions.
Ethernet, monitoring, or signalling interface	IEC 61643-21 plus IEC 61643-01:2024	Verify the actual data interface, bandwidth, power delivery, and bonding requirements.

No single product-standard number automatically covers the complete plant. The correct specification follows the protected electrical circuit.

EV Charging Equipment With AC Supply, DC Power, and Communications

An EV charging installation can include an AC input, internal or external DC power circuits, and communications interfaces. The starting classification may therefore involve Part 11 for AC, Part 41 for eligible non-PV DC power, and Part 21 for data or signalling.

However, charger-specific equipment standards, installation requirements, manufacturer architecture, and jurisdictional rules can add conditions beyond the SPD product standard. Do not assume that a generic DC SPD is automatically acceptable anywhere inside charging equipment.

Industrial Ethernet With Power over Ethernet

A cabinet may contain a 24 V DC power bus and a separate PoE Ethernet network. Although both contain DC voltage, their circuit functions differ.

• A qualifying standalone DC power distribution circuit points toward Part 41.
• A qualifying PoE telecommunications/signalling line points toward Part 21.

The applicable product part does not eliminate the need to verify system voltage, signal integrity, current, connector type, protection modes, and installation instructions.

Product Standards vs. Selection Guidance vs. Installation Standards

Another common mistake is treating every related IEC publication as the same kind of requirement.

Document category	Примеры	What it helps establish	Что он не подтверждает сам по себе
Common and application-specific SPD product requirements	IEC 61643-01, -11, -21, -31, -41	The relevant technical requirements and test framework for a defined SPD application.	That a specific installation is correctly designed or that every product carrying a standard reference has verified third-party certification.
Руководство по выбору и применению	IEC 61643-12, -22, -32	Principles for selecting, applying, locating, or coordinating SPDs in the applicable system context.	That an individual SPD model has passed an application-specific product test.
Electrical installation requirements	IEC 60364-5-53 and applicable national installation rules	Requirements governing selection and erection within an electrical installation.	That an individual product complies with the appropriate IEC 61643 product standard.
PV installation requirements	IEC 60364-7-712 and applicable national PV installation rules	Requirements associated with photovoltaic electrical installations.	That a generic DC SPD is suitable for every PV or battery circuit.

The related IEC 61643 application documents have different scopes:

• IEC 61643-12:2020 provides selection and application principles for SPDs used in AC power systems; it is not a substitute for the Part 11 product standard.
• IEC 61643-22:2015 addresses selection and application for telecommunications and signalling networks; it is not a substitute for the Part 21 product standard.
• IEC 61643-32:2017 addresses SPD selection, installation, and coordination in PV systems, including the stated PV DC and AC system contexts. Its public scope notes that installations including batteries may require additional requirements.
• IEC 60364-5-53:2019 addresses the selection and erection of relevant protective and switching equipment within low-voltage installations.
• IEC 60364-7-712:2025 addresses photovoltaic electrical installations and explicitly includes installation requirements relating to possible energy-storage systems. That installation-level inclusion does not erase the separate storage exclusion in the scope of the IEC 61643-31:2018 product standard.

For physical conductor routing, protective-device coordination, and installation checks, use the dedicated SPD wiring and installation guide rather than treating a product-standard crosswalk as a wiring procedure.

Does IEC 61643 Compliance Prove Type 1, Type 2, or Type 3 Suitability?

Not by itself. The applicable product standard identifies the relevant requirements and test framework, but an SPD’s declared classification, protection modes, test duties, and electrical ratings must be verified for the exact product.

For AC power SPDs, Type 1, Type 2, and Type 3 classifications relate to defined testing and application considerations under the relevant product framework. The applicable classification does not automatically transfer across every other product part, circuit function, or jurisdiction.

Не делайте предположений:

• Every device marked “IEC 61643” has the same test duty.
• A signal-line SPD and an AC power SPD can be compared only through a shared marketing label.
• IEC type labels automatically map one-to-one to UL installation categories.
• A Type 1, Type 2, or Type 3 label alone determines voltage suitability, fault withstand, backup protection, or installation position.

For the detailed classification comparison, see Type 1 vs. Type 2 vs. Type 3 surge protective devices.

If a project also requires North American or other regional product approval, consult the dedicated comparison of IEC 61643, UL 1449, and GB 18802 surge protection standards. Compliance under one framework should not be presented as automatic approval under another.

What an IEC Standard Reference Does—and Does Not—Prove

A standard number on a datasheet can identify the framework a manufacturer declares relevant. It does not, by itself, establish all of the following:

• The exact standard edition used for assessment.
• Whether the complete SPD, one protection mode, or an assembly was evaluated.
• Whether the tested model exactly matches the offered model.
• Whether a third-party certificate or test report exists.
• Whether the document covers the product’s intended circuit, protection configuration, and ratings.
• Whether the product is accepted under the project’s local or national rules.
• Whether the installation is correctly coordinated with its source, earthing system, and backup protection.

The IEC publishes standards; a standard reference alone is not interchangeable with a product certificate. Where project requirements demand independent evidence, request the applicable test report, certificate, issuing organization, covered model identification, standard edition, and assessment scope.

Similarly, a national or regional adoption can have its own publication date, amendments, transitional arrangements, or market requirements. The exact IEC publication, EN adoption, national designation, certificate, and contractual specification should be compared rather than assumed identical.

IEC 61643 Procurement and Engineering Verification Checklist

Before accepting an SPD specification, confirm these points for the exact device and circuit:

1. Protected-circuit function: Identify whether the circuit is AC power, PV-generator DC, other DC power, or telecommunications/signalling.
2. Applicable product standard: Match the circuit to the appropriate published IEC 61643 product part and confirm that no application-specific exclusion applies.
3. Standard edition: Record the exact year and edition rather than accepting an undated “IEC 61643 compliant” statement.
4. Part 01 relationship: Confirm whether the cited product edition expressly requires Part 01 and whether the supplier’s evidence reflects the applicable version.
5. Model identity: Match the certificate or report to the exact model number, pole arrangement, protection mode, voltage rating, and product configuration being offered.
6. Source and fault conditions: Verify system voltage, source characteristics, prospective short-circuit current, temporary overvoltage conditions, and the applicable declared short-circuit withstand/current information, such as I_sccr or SCCR where the relevant framework actually uses that designation.
7. Protection performance: Review the manufacturer’s declared maximum continuous operating voltage, voltage protection level, applicable discharge-current or impulse-current ratings, and other circuit-relevant characteristics.
8. Earthing and topology: Confirm compatibility with the real earthing system, connection arrangement, and protected conductors.
9. Backup protection and disconnection: Check any required external protective device, internal disconnector behavior, coordination conditions, and manufacturer instructions.
10. Interface requirements: For signal and PoE protection, verify connector type, data rate, insertion characteristics, line voltage, current, shielding, and supported power delivery.
11. Installation framework: Identify the relevant application guidance, installation standard, national rules, and project specifications separately from the product standard.
12. Independent evidence where required: Request the actual report or certificate, issuing organization, scope, validity conditions where stated, and any applicable regional adoption.

For interpretation of individual electrical declarations, use how to read an SPD datasheet and verify its actual specifications.

When comparing VIOX surge protective devices, provide the protected-circuit type, system voltage, earthing arrangement, prospective fault current, required standard edition, and project market so the correct product documentation can be evaluated against the actual application.

Official IEC References

1. IEC 61643-01:2024 — General requirements and test methods.
2. IEC 61643-11:2025 — SPDs connected to AC low-voltage power systems.
3. IEC 61643-21:2025 — УЗИП, подключенные к телекоммуникационным и сигнальным сетям.
4. IEC 61643-31:2018 — Requirements and test methods for SPDs for photovoltaic installations.
5. IEC 61643-41:2025 — SPDs connected to DC low-voltage power systems.
6. IEC 61643-12:2020 — Selection and application principles for SPDs connected to low-voltage power systems.
7. IEC 61643-22:2015 — Selection and application principles for telecommunications and signalling networks.
8. IEC 61643-32:2017 — Selection and application principles for SPDs in photovoltaic installations.
9. IEC 60364-5-53:2019 — Selection and erection of electrical equipment for protection, isolation, switching, control, and monitoring.
10. IEC 60364-7-712:2025 — Requirements for photovoltaic installations.

Standards scopes and publication editions verified against official IEC publication pages on August 25, 2026. Applicable national adoptions, project specifications, manufacturer instructions, and product-specific evidence must be checked for each installation.